32-32-00
ALL ú ú 01 Page 5 ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
VIEW LOOKING DOWN
Wing Gear Lock MechanismFigure 4
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32-32-00
ALL ú ú 01 Page 6 ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
B. Normal operation of the uplock hook is by hydraulic fluid directed to the uplock actuator. This latches and unlatches the hook in the proper sequence as governed by the door-operated sequence valve. Provision is made to release the uplock in the absence of hydraulic pressure by means of an electrical actuator attached to the release cam. This cam contacts a follower which releases the hook.
6. Wing Gear Uplock Actuator (Fig. 5)
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A. The wing gear uplock actuator is mounted on the uplock mechanism. It operates with hydraulic fluid controlled by the door-operated sequence valve. The actuator extends to unlock the hook and retracts to lock the hook. A schematic of this actuator is shown on figure 5.
7. Wing Gear Downlock Actuator (Fig. 6)
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A. The wing gear downlock actuator operates by hydraulic fluid controlled by the door-operated sequence valve. This actuator is mounted between the lower side strut and the lower jury strut. The actuator operates the jury strut which controls folding of the side strut. A cut-away view of the wing gear downlock actuator is shown in figure 6. The relief valve is shown exploded to clarify its operation. One of two rod end bleed plugs is also shown. You must open one of the bleed plugs, before the actuator is removed, to remove the remaining pressure from the retract side of the actuator.
8. Wing Gear Downlock Bungee
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A. The spring-type wing gear downlock bungee is installed between the upper side strut and the lower jury strut (Fig. 1). This bungee aids the downlock actuator in locking the gear down. It also provides a holding force to keep the gear in the locked position. In the alternate extension condition, when the gear drops of its own weight, the bungee pushes the jury strut overcenter to lock the gear down.
9. Wing Gear Door Actuator
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A. The wing gear door actuator provides the force required to open and close the wheel well doors. The actuator is a hydraulic piston type with an internal mechanical lock to hold the piston in the fully extended position (doors closed). Hydraulic pressure applied to open the doors normally unlocks the actuator. A manual release for the lock is provided for the alternate gear extension condition and when using the ground door release handle to open the doors on the ground. A snubbing action slows down the movement as the actuator piston approaches either end of its stroke. The cylinder end of the actuator is attached to the structure inboard of the wheel well, while the rod end is attached to the door actuator beam. The end of the beam is attached to the inboard half of the doors.
10. Wing Gear Door Safety Valve
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A. The wing gear door safety valve (modular assembly) is located on the inboard bulkhead of the wing gear wheel well. It is installed in the hydraulic actuator closed line from the wing gear door actuator to the wing gear uplock-operated sequence valve. The safety valve bypasses pressure from the door actuator during emergency gear operation or ground door release. This allows doors to open by gravity. The valve is identical to that used in the body system.
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